Golf club shaft having a steel and graphite composition

ABSTRACT

A hybrid golf club shaft composite is disclosed. The first part of the invention comprises a metal tip core with a composite material over the core extending the full length of the shaft. The second part of the invention comprises a cured composite shaft rolled and formed on a mandrel with a metallic outer shell/tube bonded over the composite shaft proximate to the tip area.

FIELD OF THE INVENTION

The present invention is directed to the field of golf club shafts. In particular, the present invention is directed to a golf club shaft that is made of a core in the shaft tip region of metal and a full-length outer shell that is constructed of a graphite or other composite material. Another use of the metal would be to secondarily bond a thin-walled metal tubular tip over the graphite shaft in the tip region.

BACKGROUND OF THE INVENTION

There has been a long felt need for improved golf club shafts. In particular, there is a long felt need for golf club shafts which provide the accuracy of steel with the distance characteristics provided by graphite or other composite materials. A metal core will reduce twisting in the tip area of the shaft. The hybrid shaft creates an ultra low torque shaft with the power of graphite.

A number of patents have issued to the field of golf club shafts. Japanese Patent No. 9,266,967 discloses the surface of a material tube for a golf club shaft which is applied by multilayer metal plating to plate a thin metal film on the whole surface of the shaft to reduce torsion. For this processing, the surface is sufficiently degreased and washed with water to be activated at first, then a copper plating of the first layer is formed. Next, after water washing and surface activating processing, a nickel plating of the second plating layer is formed, following that, after sufficient water washing, a finishing plating of the third layer is formed, and finally water washing and drying are carried out to complete the desired golf club shaft.

U.S. Pat. No. 6,729,970 discloses a hybrid golf club shaft set that includes a composite shaft subset including shafts formed entirely of composite, a composite/metal shaft subset including shafts formed of composite/metal combination shafts, and a metal shaft subset including shafts formed entirely of metal. The composite shaft subset preferably includes the long irons with the lowest lofts such as the two, three, and four iron shafts. The composite/metal shaft subset preferably includes the middle irons with medium lofts such as the five, six, and seven iron shafts. The metal shaft subset preferably includes the short irons with the highest lofts such as the eight, nine, and wedge shafts.

U.S. Pat. No. 6,203,447 discloses an athletic apparatus such as a golf shaft that includes a first tubular segment, a second tubular segment, and a bond apparatus to couple the first and second tubular segments. The first segment includes an inner surface defining a passage. The second segment is a shoulder and projection extending axially from the shoulder. The projection defines a bonding surface and extends into the passage. The bond apparatus is between the bonding surface and the inner surface of the first segment. The bond apparatus includes an adhesive coupling the first tubular segment to the second tubular segment and a separation element engaging the inner surface of the first segment and the bonding surface of the second segment to maintain at least a predetermined separation distance between the inner surface and bonding surface.

U.S. Pat. No. 5,993,328 discloses a hollow golf club shaft including a plurality of diverging and converging substantially frustoconical sections. The sections have respective predetermined substantially constant wall thicknesses.

U.S. Pat. No. 5,984,804 discloses a lightweight shaft that includes a plurality of non-metallic fibers arranged in prescribed orientations from one end of the shaft to the other and carried by a cured plastic material. Additional fibers are carried by the cured plastic material and are located at a butt end of the shaft to form a strengthening band which precludes splitting and cracking of the shaft at the butt end. A lightweight filler element, which is composed of a rigid foam material, is located within a portion of an opening at a tip end of the shaft to strengthen the tip end.

U.S. Pat. No. 5,882,268 discloses a golf club that includes a shaft with a grip assembled on a butt end of the shaft. A club head is mounted on a tip end of the shaft. The shaft is composed of a non-metallic material, such as fibers in a cured plastic matrix, and is formed with a tapered intermediate section. The section includes two segments which taper at different taper rates. A bulge is formed in the shaft near an inboard extremity of the tip end. The bulge is formed with a central cylindrical section and transition sections on opposite axial ends of the central section. The diameter of the bulge at any cross section thereof is greater than the diameter of the immediately adjacent portions of the shaft. Also, the bulge is formed with an axial opening, the diameter of which is less than the diameter of the immediately adjacent portions of the shaft.

U.S. Pat. No. 6,280,347 discloses a golf club shaft is provided with ring-like shaft stiffening bodies at a given location along the shaft in order to locate the shaft flex point appropriately for a particular individual. Each stiffening body consists of a quantity of an epoxy and glass fibers mixture which is molded about the shaft and sets up to a rigid condition.

U.S. Pat. No. 6,132,323 discloses an improved shaft for a golf club and methods of manufacturing the same. A plurality of layers of composite fiber bound within a thermoset resin are bonded to one or more layers of composite fiber bound within a thermoplastic resin using a high peel strength nylon epoxy adhesive. Preferably, the layer(s) of composite fiber bound within the thermoplastic resin comprise the outermost layer of a golf club shaft. In one preferred form, a plurality of plies of pre-preg composite sheet including a thermoset resin are wrapped around a mandrel and pre-cured. Thereafter, a layer of adhesive is wrapped over the pre-cured plies, at least one ply of pre-preg composite sheet including a thermoplastic resin is wrapped over the adhesive, and a cellophane or polypropylene tape is wrapped over the outermost layer of pre-preg. Thereafter, the ply wrapped mandrel is placed in a mold and heated to a predetermined temperature for a time sufficient to allow curing of all of the plies comprising the golf club shaft. In an alternative form, the layer of fiber comprising the thermoplastic resin may be pre-cured and used as a shell during the curing process. Bladder molding is preferred in such embodiments.

U.S. Pat. No. 6,692,377 discloses to an improved golf club shaft. The golf club shaft includes a shaft body made of a composite material, such as carbon/epoxy, and a metal foil wrapped in a spiral pattern around at least a portion of the shaft body. The metal foil increases the torsional stiffness of the shaft and improves its bending stiffness, thereby enabling the first and second frequencies of a golf club employing the shaft to remain in a desired range.

U.S. Pat. No. 4,157,181 discloses a novel structural member, such as a golf club shaft or other tapered tubular member, having an unusually high resistance to torsional deflection for given desired longitudinal deflections along with high strength and a center of gravity more favoring the tip-end is provided by a resin-bonded graphite fiber structure in which the fiber orientations in each layer of the multi-layer, composite structure are varied along the length of the shaft and in desired orientation relationships between layers to achieve the unique combination of properties. This structural member is prepared by helically placing fiber yarns such as graphite onto a resin-coated, tapered steel mandrel by winding a series of high modulus graphite yarns in series of layers and progressively varying the rotational speed of the rings carrying the spools of the graphite fiber yarns in each layer as the mandrel is fed at a constant speed. The continuously varying rotational speeds of these rings and the wrapping angles to which the yarns are applied to the mandrel result in a unique structure achieved by optimizing the wrapping angles in each layer at desired progressive changes in fiber orientation different in each layer, and from layer to layer in the structure.

U.S. Pat. No. 5,505,447 discloses a golf putter having a flexible hosel between the shaft and the blade. A rigid canopy covers the distal end of the shaft and the proximal end of the hosel, thereby coupling the two. The hosel may be split into two flanges or may be a single, solid piece and is preferably made of graphite or spring steel. When the blade strikes the golf ball, the hosel is deformed and thereby stores energy from the stroke which is normally lost to noise, shaft vibration and blade rebound. The spring nature of the hosel returns the deformed hosel to its quiescent state, thereby imparting the stored energy to the ball in the line of the putt. The amount of deformation experienced by the hosel is controlled by the amount of the hosel covered by the canopy.

U.S. Patent Application No. 2002/0187850 discloses a method for altering a graphite golf club shaft having a hollow interior with an interior wall surface, a butt end, and a flex zone sixteen inches from the butt end with a range one inch up and one inch down from the measured sixteen inch point which includes placing a section of steel tubing into the hollow interior shaft and against the interior wall surface in the flex zone.

Canadian Patent Application No. 2,231,908 discloses a shaft of the present invention is formed as an axially elongated member for use in sports equipment, such as golf clubs, fishing rods or the like. The shaft is made from composite polymers, such as a graphite composite and includes an outer sidewall which extends radially about an axis to define a substantially hollow or resin filled core. At least part of the core is divided into two or more longitudinally extending cavities by a reinforcing web or member which spans radially separate points along the shaft sidewall. The reinforcing member is preferably axially elongated anti extends at least part way along the portion of the shaft. The position of the reinforcing member is oriented in the shaft to increase the shaft rigidity against bending in the direction of bending, load and/or impact forces.

Heretofore, there has not been an effective system which joins the benefits of steel and graphite in golf shafts. Such a shaft would enable a user to achieve the power of graphite with the control of steel.

It is an object of the present invention to provide a novel golf club shaft which has a metal core composite and which includes an anisotropic material such as graphite.

It is a further object of the present invention to provide a hybrid golf shaft which contains either an outer core or an inner core of an anisotropic material.

It is a further object of the present invention to provide a unique hybrid golf club shaft comprising steel and graphite.

These and other objects of the present invention will become apparent from the detailed description which follows.

SUMMARY OF THE INVENTION

In accordance with the present invention, a hybrid golf club shaft comprising: a tapered tube metal core draft extending a portion of the way up a shaft; and a shaft material overlaying the tapered tube metal core and cured to the tapered tube metal core. The hybrid golf club shaft has a tapered tube metal core with variable length.

In a further embodiment, the invention is a hybrid golf shaft composite comprised of a cured composite shaft rolled and formed on a mandrel; and a tapered metal shell tube that is secondarily bonded over the composite shaft proximate to the tip area of the shaft.

In a yet further embodiment, the invention is a hybrid golf shaft comprising a hybrid shaft core tube section designed to be affixed to the tip end of a golf club shaft; and a prepreg steel shaft rolled over the core and core-cured therewith.

BRIEF DESCRIPTION OF THE FIGURES

FIGS. 1 to 5 are a perspective view of the components of a first embodiment of the present invention.

FIGS. 6 to 10 are a perspective view of an alternative embodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention is described with reference to the enclosed Figures wherein the same numbers are used where applicable. The invention comprises a golf shaft comprising and including an anisotropic composite layer such as constructed from graphite. The composite allows the shaft to flex more than a steel shaft.

The graphite crystal is one of the most anisotropic (meaning exhibiting properties with different values when measured along axes in different directions) bodies known. Anisotropy is the direct result of the layered structure with extremely strong carbon-carbon bonds in the basal plane. Properties of graphite crystals illustrating this anisotropy are shown in Table 1. Of particular interest for the electronics cooling market is the very high basal plane thermal conductivity (˜2000 W/mK) achievable in single crystal graphite. TABLE 1 Properties of Graphite Crystals at Room Temperature Property Value in Basal Plane Value Across Basal Plane Resistivity · m 0.40 ˜60 Elastic Modulus GPa 1020 36.5 Tensile Strength (est.) GPa 96 34 Thermal Conductivity W/mK ˜2000 10 Thermal Expansion oC-1 −0.5 × 10-6 27 × 10-6

Referring to FIG. 1, the invention is directed to a hybrid golf shaft 10. The purpose of the invention is to provide a golf club which combines the accuracy of steel with the distance of graphite. A metal core reduces twisting in the tip of the shaft and creates an ultra-low torque shaft. The shaft's kick point is governed by the graphite or composite in order to retain distance and feel. Hence, the mid and butt portions of the shaft are constructed from an anisotropic material such as graphite to retain strength. The insert (core) may be either longer or shorter, as required.

The structure of the present invention is now described. The golf shaft manufacturing methods comprises a rolling mandrel core 1 which is stepped 12 to accept a metal core tube 14. FIG. 2 illustrates a hybrid shaft metallic core rube 14 comprising anisotropic graphite. The metallic core can be of varying length to meet different design parameters, and fits over the mandrel 10.

FIG. 3 illustrates the mandrel 10 with the shaft core 14 in place. FIG. 4 illustrates a pre-preg shaft material 16. The shaft 16 is rolled over the core 14 and co-cured. FIG. 5 illustrates a tip section view of the graphite on the outside of the metal core showing core 14 and pre-peg shaft 16.

FIG. 6 illustrates another embodiment of the invention in which a pre-preg shaft material 18 is rolled and cured on a mandrel as shown in FIGS. 7 to 9. A cured composite shaft 20 is then co-bonded. A metallic outer shell tube 22 comprising anisotropic material is then placed on the shaft. A cured shaft with metal shell bonded in the tip area is thus provided.

The present invention has been described with reference to the above-discussed preferred embodiment. It is to be appreciated that the true nature and scope of the invention is to be determined with reference to the claims attached hereto. 

1. A hybrid golf club shaft comprising: a metal core tube extending a portion of the way up a shaft; a shaft material overlaying the metal core and cured to the metal core.
 2. The hybrid golf shaft of claim 1 wherein the length of the metal core has a variable length.
 3. A hybrid golf club shaft composite comprising; a cored composite shaft rolled and formed on a mandrel; and a metal outer shell/tube bonded over the composite shaft proximate to the tip area.
 4. A hybrid golf shaft comprising: a hybrid shaft core tube section designed to be affixed to the tip end of a golf club shaft; and a prepreg steel shaft rolled over the core and cured therewith. 